The field of the present invention is product discrimination systems based on color.
Fruit and vegetable products have been subject to sorting based on color in the past. Initially, such tasks were performed manually. More recently, as labor continues to be more and more expensive and unavailable, machine sorting by color has been attempted. A device capable of sorting by color is described in U.S. Pat. No. 4,106,628 to Warkentin et al., the disclosure of which is incorporated herein by reference. In this system, color from a product unit is directed through lenses, fiber optics and filters to a sensing mechanism. In the actual system, light from both sides of a product unit was gathered in a single scan per product unit by two bundles of optic fibers looking from opposed sides of the product unit. Each optic fiber bundle was split and combined with a respective split portion of the other bundle. Therefore, each resulting optic fiber bundle had light from both sides of the product unit. Filters of different wavelength capacity were employed to filter the light derived from the resulting two fiber optic bundles. Red and green filters were given as examples, one filter for each resulting bundle. The signals generated by the filtered light were then compared with a standard such that a red/green color classification could have been made based on the readings compared with the standard.
More complicated sensing devices have been developed which use line scan cameras for determining such attributes as cross-sectional area. Such cameras have used light to present pixel information which may then be processed for summation and the like. For example, cross-sectional area may be determined by counting the number of pixels registering presence of the product unit. In order to detect color using such a system, a very complicated system would be required because of the substantial amount of data to be received and processed. With product units traveling at any reasonable speed past such a discrimination system, it quickly becomes impossible to keep up with the processing of relevant information without a very substantial data processing system. Further, being constrained to pixel units does not afford adequate latitude in controlling sensitivity.
Difficulties have been encountered in distinguishing between product units which are juxtaposed or overlapping. Recognition of two or more products so situated has been accomplished by noting decreases followed by increases in width. Noting substantial deviations from a length to width ratio of unity has also been used for such product unit recognition. However, irregular shaped units and elongated units have not lent themselves to discrimination using such processes.